Indogen thickened grease composition



Patented May 25, 1954 INDOGEN THICKENED GREASE COMPOSITION Cecil G. Brannon, Munster, and Edward A. Swakon, Hammond, Ind., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application November 1, 1952,

Serial No.

9 Claims.

The present invention relates to novel lubricant greases and to the method of preparing same. More particularly, it relates to novel greases comprising a lubricant vehicle thickened with certain high melting indogen compounds, specifically those melting above about 250 F. Greases of this type, particularly those wherein the lubricant vehicle comprises a silicone polymer oil, have demonstrated exceptional stability and lubricity at elevated temperatures.

As lubricants are required to perform at higher and higher temperatures because of increased speeds of engines and machines, the advent of jet propulsion, atomic energy as a source of power, etc., it has become increasingly difiicult to prepare greases fulfilling the requirements of such lubricants. In attempting to provide such greases, the art has progressed from the use of petroleum lubricant vehicles thickened with metal soaps of long chain fatty acids, e. g. lithium hydroxystearate, to more thermally stable synthetic lubricating oils such as the aliphatic diesters of dicarboxylic acids, silicone polymers, etc., thickened with such soaps or inorganic materials such as silica gels, etc. The progress of thickener research has not in general, however, kept pace with the development of lubricant vehicles. And at operating temperatures as high as 400 to 450 able which will retain their consistency and lubricity for any substantial period of time.

In recent years various synthetic lubricant vehicles, e. g. the silicone polymers, fluorocarbons, etc., have been found potentially valuable for use in greases employed at very high temperatures because of their thermal stability and relatively low volatility. Unless, however, a thickener having substantially the same degree of thermal stability is available to produce a grease from such an oil, they are of little use.

In accordance with the present invention high melting indogen compounds, i. e. heterocyclic compounds such as indigo, isoindigo, isatin, isatide, etc., may be employed to thicken various oleaginous vehicles to produce greases which are stable and display excellent lubricant properties at high temperatures. Compounds of this type having a melting point above about 250 F. are contemplated for use in accordance herewith. Silicone polymer oils are particularly preferred for use in greases employed at temperatures as high as about 450 F. Other lubricant vehicles, either natural or synthetic, may also be thickened with such materials to produce greases particularly suited for use at temperatures between about 250 and about 400 F.

F. there are few if any greases avail- It is a primary object of the present invention to provide lubricant greases which are stable and give excellent lubrication at temperatures above about 250 F. A further object is to provide a readily producible series of greases embodying a novel class of thickening agents capable of yielding lubricants particularly suitable for use at temperatures from about 250 F. to about 450 F. A particular object of the present invention is to provide greases which are effective lubricants at temperatures as high as about 450 F. for substantial periods of time. These and additional objects will be apparent from the following detailed description.

We have found that lubricating vehicles such as silicone polymer oils, mineral lubricating oils derived from petroleum, synthetic lubricating oils such as fluorocarbons, polyalkylene glycols and their derivatives, high molecular weight esters of di-carboxylic acids, etc. and preferably the silicone polymer oils, may be thickened to grease consistency by the addition thereto of from about 10 to about and preferably from about 20 to about 50% of an indogen compound melting above about 250 F.

Thus, in accordance herewith, those compounds melting above about 250 F. which contain either of the structures shown empirically below are contemplated as thickening agents in the art of grease manufacture and shall be referred to broadly herein and in the appended claims as indogen compounds:

In the above formulae, R and R represent aryl or alkyl aryl radicals which are linked to the adjoining members of the heterocyclic rings by bonds disposed in ortho relation. These radicals may be the same or different and may be mono or poly cyclic, e.'g. phenylene, biphenylene, naphthylene, etc. These aryl or alkyl aryl radicals may be substituted radicals, containing various substituents such as hydroxy, carboxy, halo, nitro, etc. Examples of such compounds are indigo, iso-indigo, 3-keto-indoline, isatide, isatin, etc. It should be understood that these specific examples are enumerated for purposes of illustration and not of limitation.

The silicone polymer oils which may be employed in accordance with the present invention are those falling substantially within the lubriliquid SOz, nitrobenzene, etc.

cating oil viscosity range. In general, such oils have the following unit structure:

wherein R and B may represent substituted or: unsubstituted alkyl, aryl, alkyaryl, aryalkyl or cycloalkyl groups. Such compounds maybe pro-'- duced by well-known methods, e. g. the hydrolysis of dialkyldichlorosilanes or. dialkyldiethoxy silanes with a suitable chain stopper, e. g. a trisubstituted monochlorosilane; For purposes of the present invention, only those polymers which are high boiling liquids withinthe lubricating oil viscosity range are suitable, these-generally, possessing a viscosity at 100 F. which is within the range of from about 25 to about 3500 SZS.U. It is preferred, for purposes hereof, to employ such oils as have a viscosityat 100 F. of from about 300 S. S. U. to about 1250 S. S. U. Suchproducts are generally colorless and inert, havea. very low volatility and undergo relatively slight. change in viscosity for a given change in tem-- perature. Relatively common oils of this type are dimethylsilicone polymer, phenylmethylsilicone polymer, chlorophenylmethylsilicone poly-- mer, etc., it being preferred to employ the phen-s ylinethylsilicone polymer in accordance herewith. Method of preparing such compounds are.

taught in numerous patents, e. g. U. S. 2,410,346, U. S. 2,456,496, and in the literature suchas. Chemistry of the Silicones byRochow, page 61, et seq. A particularly desirable phenylmethylsilicone polymer the present invention is Dow-Corning 550 silicone fluid, a product of Dow-Corning, Inc., which has a viscosity at 100 F. of about 300 to about 400. S. S. U.

Other oleaginous vehicles which may be employed herewith are, for example, mineral oils in the lubricating oil viscosity range, i. e. from about 80 S. S. U. at 100 F. to about 300 S. S. U. at210 F. These mineral oils are preferably solvent extracted to remove substantially the low V. I. constituents, e. g. aromatics, with phenol, furfural, BB dichlorodiethylether(Chlorex), Synthetic lubri eating oils resulting from polymerization of un. saturated hydrocarbons or other oleaginous materials within the lubricating oil viscosity rangesuch as high molecular weight polyoxyalkylene compounds such as polyalkylene glycols and esters thereof; aliphatic diesters of dicarboxylic acids such as the butyl, hexyl, Z-ethylhexyl,

decyl, lauryl, etc; esters of sebacic acid, adipic acid, azelaic acid; fluorocarbons, etc.; may be thickened by the indogen compounds of the present invention to produce excellent greases.

Greases of the present invention may be produced by any of the usual grease making techniques such as mixing thickener and oil and thenmilling the mixture in a colloid mill, 3-rollmill, etc. The thickener may be added to the vehicleas such or the reactants may be added and the thickener produced in situ. As a-step in anyof the usual techniques improved properties may beimparted to the grease comprising asilicone vehicle by heat-treating the grease-mixture, ice.

subjecting same to a temperature of about 450 F. for at least about half an hour and preferably longer, e. g. from about 1 to 20 hours. Prolongedv heating at such temperature may evaporate a portion of the lubricant vehicle; this loss should be replaced and then the mixture should be for use in accordance with 4 milled. If desired, the heating and readdition of vehicle may be repeated before milling.

A typical grease of the present invention was prepared by mixing '7 grams of D0550 (phenylmethyl silicone polymer oil product of Dow- Corning, Inc. having a methyl-phenyl ratio of about 0.6 and a viscosity in the range of from about 300 to about 400 S. S. U. at 100 F.) with 15? grams of 'a" 20% (by weight) indigo paste. This'mixture was agitated in a beaker and heated while stirringuntil the temperature of the mixture was above about 300 F. The mixture was thereafter cooled and milled in a 3-roll mill. The resulting grease was smooth and had a consistency of N. L. G. I. No. 1 grade. The grease soprepared was then tested in the A. B. E. C.- Ni L. G. I. high speed high temperature bearing test. (hereinafter described in detail). At 450 and 10,000 R. P. running in cycles of 20 hours operating and 4 hours at rest, the grease lubricated the bearing for 427 hours before failure.

The bearingtest referred to above is a tenta-- tive one adopted by the Coordinating Research Council during the. last World War and is generally referred to as the A. B. E. C.-N. L. G. I. test. It is conducted as follows: 3 grams of grease are placed in each of two bearings disposed on the test spindle. One bearing, a special heat treated precision 204 Norma-Hoffman bear ing, is subjected to a temperature of 450 F. in an oven, the other bearing, a standard New Departure 204 bearing, is at room temperature. Temperature is determined by a thermocouple inserted .in the grease between the races of the bearing in the oven. Failure is adjudged to occur when (1) the temperature in the test bear ing reaches 470" F. or higher, (2) wattage in excess of 300% of normal wattage as required,

' 012(3) thebearing does not turn over at the be- 'torily in the preparation of greases,

ginning of a test cycle (the test is conducted incycles of, 20 hours operating and 4 hours at rest).

The paste preparation comprising 20% indigo, referredto above, is .a commercially available product ofNational Aniline Division of Allied. Chemical and Dye Corporation. The paste comprises 20% of indigo by weight and 80%. of water. This material may be employed satisface as indicated, or pure indigo itself, not in paste form, may beemployed. Thus, for example, a grease was. prepared by mixing 3.6 grams of indigo with 8.4 grams of.DC550 silicone oil in a beaker. The.

smoothbuttery blue grease resulting from mil-- ling this mixture in a 3-roll mill had a consistency of an N. L. G. I. No. 0 grade.

Greases prepared by thickening oleaginous materials such as polyalkyleneoxide compounds, diesters of dicarboxylic esters, etc., with indigo or.the like are stable at high temperatures although generally these greases are somewhat less stable thanthose prepared with silicone oil or, fluorocarbons as the lubricant vehicle. Accordingly, they aremore suitably employed in .the' range of 250 F. to about 400 F. It should be understood, in any event that while the greases of the present invention are particularly suitable for use at temperatures above 250 F., they may be employed for many purposes at lower temper-- aturesand with excellent results. These greasesmay have added thereto anti-oxidants, oiliness agents, extreme pressure additives, etc. without in any way departingfrom the scope of the present 75' invention.

Having thus described our invention, what we claim as novel and desire to protect by Letters Patent is defined by the following claims:

1. A lubricant grease comprising essentially a lubricant vehicle thickened with an amount of from about 10% to about 70% by weight of an indogen compound melting above about 250 F.

2. The lubricant grease of claim 1 wherein the lubricant vehicle comprises a silicone polymer oil in the lubricating viscosity range.

3. The lubricant grease of claim 2 wherein the silicone polymer oil comprises a phenyl-methyl silicone polymer oil in the lubricating oil viscosity range.

4. The lubricant grease of claim 1 wherein the lubricant vehicle comprises an acyclic ester of an aliphatic di-carboxylic acid in the lubricating oil viscosity range.

5. The lubricant grease of claim 1 wherein the lubricant vehicle comprises a polyoxyalkylene compound in the lubricating oil viscosity range.

6. The lubricant grease of claim 1 wherein the lubricant vehicle comprises a polyfiuoro-compound in the lubricating oil viscosity range.

7. A lubricant grease comprising essentially a lubricant vehicle thickened with an amount of from about 10 to about 70% by weight of indigo.

8. The lubricant grease of claim 7 wherein the lubricant vehicle is a silicone polymer oil in the lubricating oil viscosity range.

9. The lubricant grease of claim. 8 wherein the silicone polymer oil is a phenyl-methyl silicone polymer oil.

No references cited. 

1. A LUBRICANT GREASE COMPRISING ESSENTIALLY A LUBRICANT VEHICLE THICKENED WITH AN AMOUNT OF FROM ABOUT 10% TO ABOUT 70% BY WEIGHT OF AN INDOGEN COMPOUND MELTING ABOVE ABOUT 250* F. 